In a photoelectric conversion apparatus described in FIG. 2 of PTL 1, an amplification transistor (which is denoted by a reference symbol 114 in FIG. 2) of a pixel and a differential transistor (which is denoted by a reference symbol 201 in FIG. 2) arranged in each column constitute a differential amplifier. A signal based on charges generated in a photoelectric conversion element is input to the amplification transistor of the pixel. A reference voltage having a ramp waveform is input to the differential transistor. Then, through an operation of comparing a voltage at a gate of the amplification transistor of the pixel with a voltage at a gate of the differential transistor, the signal based on the charges generated in the photoelectric conversion element is converted into a digital signal.